1. Field of the Invention
The invention relates to method and apparatus for the winding of coils of filamentary material in a figure 8 winding configuration and, more particularly, to such method and apparatus in which the density of the wound coil or package is controlled to increase the density of the wind. The invention has application to figure 8 winding configurations and in particular to figure 8 winding configurations of filamentary material in which a radial hole (payout hole) is produced from the innermost wind to the outermost wind, thereby enabling the filamentary material to be withdrawn from inside the wound coil through the payout hole to eliminate kinking or bird-nesting of the filamentary material as it is paid out. The winding techniques are known in the winding trade as REELEX® or REELEX II® winding processes and are the subject of trademark and patent protection by Windings, Inc., the assignee of the present invention.
2. Related Art
Known technology for winding filamentary material in a figure 8 configuration on a mandrel produces figure 8 coils substantially evenly spaced radially around the mandrel. Each layer of the wound coil is produced by advancing the figure 8s in either a plus direction (plus ADVANCE or upper ratio), or in the minus direction (minus ADVANCE or lower ratio). A plus or negative ADVANCE refers to changing the speed of rotation of the mandrel with respect to the movement of the traverse which is feeding the filamentary material to the mandrel. This concept was introduced as early as 1956 in U.S. Pat. No. 2,767,938; Taylor, Jr.; “Winding Flexible Material”; assigned to Windings, Inc. the assignee of the present invention.
The ADVANCES have also been referred to as “gear ratios”, which can be actual mechanical gears (prior technology), or more recently, “electronic gears”. In the latter method, for example, computer-generated signals control the rotation of the spindle on which the mandrel is mounted with respect to the movement of the traverse to obtain the desired ADVANCE. The wound layers of filamentary material are produced by alternating between the aforementioned positive or negative ratios. In the REELEX® or REELEX II® winding technique of Windings, Inc. a portion of the wound coil is devoid of the figure 8s to generate the aforementioned radial payout hole for deploying the wound filamentary material.
In prior or known winding techniques the ADVANCES are set and remain fixed throughout the production of the entire wound coil. Because the number of figure 8s in each layer is constant (in alternating layers) it is apparent they are spaced circumferentially further apart as the coil diameter increases as the winding process continues. This has the effect of decreasing the density of the wound coil as the diameter of the coil increases. For example, if the figure 8s are spaced 36 degrees apart in one of the layers (10 figure 8s in the particular layer), the figure 8s will be approximately 2.4 inches apart (along the circumference of the wind) on the surface of a mandrel that is 8 inches in diameter. The figure 8s will be 4.8 inches apart when the coil reaches 16 inches in diameter and 6.6 inches apart when the coil reaches 21 inches in diameter. A similar result is of course obtained with other spacing of the figure 8s and mandrels of different diameter.